Process for depigmenting keratin materials using thiopyridinone compounds

ABSTRACT

Provided is a nontherapeutic cosmetic process for depigmenting, lightening and/or whitening keratin materials applying an effective amount of at least one compound of formula (I): 
                         
or a tautomer thereof of formula (I′):
 
                         
to a keratin material, where the structural variables are as defined herein.

The present invention relates to a cosmetic treatment process in particular for depigmenting and/or whitening the skin, that employs at least one compound of thiopyridinone type.

At various periods in their life, certain people develop darker and/or more coloured marks on their skin, and more especially on the hands, which gives the skin a heterogeneous appearance. These marks are due in particular to a high concentration of melanin in the keratinocytes located at the surface of the skin.

The use of harmless topical depigmenting substances which exhibit good efficacy is especially desirable with a view to treating pigmentary marks.

The mechanism of formation of skin pigmentation, i.e. of the formation of melanin, is particularly complex and involves, schematically, the following principal steps:

-   Tyrosine--->Dopa--->Dopaquinone--->Dopachrome--->Melanin

Tyrosinase (monophenol dihydroxyl phenylalanine: oxygen oxidoreductase EC 1.14.18.1) is the essential enzyme involved in this series of reactions. It catalyzes in particular the reaction converting tyrosine to Dopa (dihydroxyphenylalanine) by virtue of its hydroxylase activity, and the reaction converting Dopa to dopaquinone by virtue of its oxidase activity. This tyrosinase acts only when it is in the mature form, under the action of certain biological factors.

A substance is acknowledged to be depigmenting if it acts directly on the vitality of epidermal melanocytes, where melanogenesis takes place, and/or if it interferes with one of the steps of melanin biosynthesis, either by inhibiting one of the enzymes involved in melanogenesis, or by being inserted as a structural analogue of one of the chemical compounds of the melanin synthesis chain, which chain may then be blocked and thus ensure depigmentation.

Arbutin, niacinamide and kojic acid are known as skin depigmenting agents.

Substances have been sought which exhibit an effective depigmenting action, in particular greater than that of arbutin, niacinamide and kojic acid.

In this regard, the applicant has found, surprisingly and unexpectedly, that certain thiopyridinone compounds exhibit good depigmenting activity, even at low concentration.

The subject of the invention is therefore a nontherapeutic cosmetic process for depigmenting, lightening and/or whitening keratin materials, in particular the skin, which comprises the application of a cosmetic composition comprising, in a physiologically acceptable medium, at least one compound of formula (I) as defined hereinafter.

The invention also relates to the nontherapeutic cosmetic use of a compound of formula (I) as a whitening, lightening and/or depigmenting agent for keratin materials, in particular the skin.

The compounds used according to the invention allow effective depigmenting and/or lightening, or even whitening, of the skin of human beings. They are in particular intended to be applied to the skin of individuals exhibiting brownish pigmentation marks or senescence marks, or to the skin of individuals who wish to combat the appearance of a brownish colour arising from melanogenesis.

They may also allow depigmentation and/or lightening of body hair, the eyelashes, head hair and also the lips and/or the nails.

The compounds used according to the invention therefore correspond to formula (I) or (I′) below:

in which:

-   R₁ and R₂, which may be identical or different, denote a radical     chosen from:     -   a) a hydrogen atom;     -   b) a saturated linear C₁-C₂₀ or branched C₃-C₂₀ or unsaturated         C₂-C₂₀ alkyl group, optionally interrupted with one or more         heteroatoms chosen from N, S and O, and/or optionally         substituted with one or more groups, which may be identical or         different, chosen from:         -   i) —OR₃         -   ii) —SR₃,         -   iii) —NR₃R₄         -   iv) —CONHR₃         -   v) —COOR₃;         -   vi) a C₅-C₁₂ aryl group optionally substituted with one or             more hydroxyls and/or with one or more C₁-C₈ alkoxy             radicals;     -   c) a saturated C₁-C₈ alkyl group substituted with a C₅-C₁₂ aryl         radical optionally substituted with one or more hydroxyls and/or         with one or more C₁-C₈ alkoxy radicals;     -   d) a phenyl group optionally substituted with one or more         hydroxyls and/or with one or more C₁-C₈ alkoxy radicals; -   R₃ denoting a hydrogen atom or a saturated linear C₁-C₅ or branched     C₃-C₅ or unsaturated C₂-C₅ hydrocarbon-based group, -   R₄ denoting a hydrogen atom; a saturated linear C₁-C₅ or branched     C₃-C₅ hydrocarbon-based group; or an acetyl group;

it being possible for R₁ and R₂ to form, with the nitrogen atom which bears them, a ring chosen from pyrrolidine, pyrroline, piperidine, piperazine, morpholine, thiomorpholine and azepine;

and also the salts thereof, the solvates thereof and the optical isomers thereof, and the racemates thereof.

The compound (I′) is the tautomer form of the compound (I) when a tautomeric equilibrium exists according to the following scheme:

The salts of the compounds of formula (I) or (I′) comprise the conventional nontoxic salts of said compounds, such as those formed from acid or from base.

As salts of the compound of formula (I) or (I′), when it comprises a quaternizable nitrogen atom), mention may be made of:

-   a) the salts obtained by addition of the compound (I) or (I′) with     an inorganic acid, in particular chosen from hydrochloric acid,     boric acid, hydrobromic acid, hydrioic acid, sulphuric acid, nitric     acid, carbonic acid, phosphoric acid and tetrafluoroboric acid; -   b) or the salts obtained by addition of the compound (I) or (I′)     with an organic acid, in particular chosen from acetic acid,     propionic acid, succinic acid, fumaric acid, lactic acid, glycolic     acid, citric acid, gluconic acid, salicylic acid, tartaric acid,     terephthalic acid, methylsulphonic acid, ethylsulphonic acid,     benzene-sulphonic acid, toluenesulphonic acid and triflic acid.

Mention may also be made of the salts obtained by addition of the compound of formula (I) or (I′) (when it comprises an acid group) with an inorganic base, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonium hydroxide, magnesium hydroxide, lithium hydroxide, and sodium, potassium or calcium carbonates or hydrogen carbonates, for example;

or with an organic base, such as a primary, secondary or tertiary alkylamine, for example triethylamine or butylamine. This primary, secondary or tertiary alkylamine may comprise one or more nitrogen and/or oxygen atoms and may therefore comprise, for example, one or more alcohol functions; mention may in particular be made of 2-amino-2-methylpropanol, ethanolamine, triethanolamine, 2-dimethylaminopropanol, 2-amino-2-(hydroxymethyl)-1,3-propanediol and 3-(dimethylamino)propylamine.

Mention may also be made of amino acids such as, for example, lysine, arginine, guanidine, glutamic acid or aspartic acid.

Advantageously, the salts of the compounds of formula (I) or (I′) (when it comprises an acid group) may be chosen from alkali metal salts or alkaline earth metal salts, such as sodium, potassium, calcium or magnesium salts; and ammonium salts.

Advantageously, the salts of the compounds of formula (I) or (I′) (when it comprises a quaternizable nitrogen atom) can be chosen from halides such as chloride or bromide; and citrates, acetates, succinates, phosphates, lactates and tartrates.

The acceptable solvates of the compounds described in the present invention comprise conventional solvates such as those formed during the preparation of said compounds as a result of the presence of solvents. By way of example, mention may be made of the solvates resulting from the presence of water or of linear or branched alcohols such as ethanol or isopropanol.

The optical isomers are in particular enantiomers and diastereoisomers.

Preferentially, the linear or branched groups can be chosen from: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl.

More preferentially, the saturated linear or branched alkyl groups can be chosen from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl and octyl.

Preferentially, the C₁-C₄ alkoxy groups can be chosen from methoxy, ethoxy, propoxy and butoxy, and even more preferentially methoxy.

The compounds of formula (I) can be obtained, in a known manner, by reacting 2-mercaptonicotinic acid and an amine of formula HNR₁R₂ (R₁ and R₂ having the meanings described above), in particular in the presence of a base such as carbonyldiimidazole.

The compounds of formula (I) can also be obtained, in a known manner, by reacting 2-mercaptonicotinic acid or 2-chloronicotinic acid with an amine of formula HNR₁R₂ (R₁ and R₂ having the meanings described above), in particular in the presence of an agent for activating carboxylic acids according to the conventional methods for activating acids (described, for example, in Comprehensive Organic Transformation by R. Larock, published by Wiley VCH, in the chapter Interconversion of nitriles, carboxylic acids and derivatives). Use is preferably made of an agent for activating carboxylic acids which makes it possible to form an acid chloride (for example, using thionyl chloride or oxalyl chloride, or 1-chloro-N,N,2-trimethyl-1-propenamine) or to form a mixed anhydride (using alkyl chloroformates), or carbodiimides or diethyl cyanophosphate are used to form carbamimidates or acylphosphonates (Phosphorus in organic synthesis-XI, Amino acids and peptides-XXI, Reaction of diethyl phosphorocyanidate with carboxylic acids. A new synthesis of carboxylic esters and amides, Tetrahedron, 32, 1976, 2211-2217). When 2-chloronicotinic acid is used as starting reagent, the chloroamide obtained is then used in an exchange reaction between chlorine and sulphur by means of reagents such as NaSH, thiourea, sodium thiosulphate or thioacetic acid (in basic medium).

Compounds of formula (I) or (I′) are described in the following documents: EP-A-298752, WO03/014062, EP-A-298752, FR-A-2349591, EP-A-2555450, WO 03/014062 and WO 2008/012532, and in the publications

-   -   article A. Monge, V. Martinez-Merino; Synthesis of 2-substituted         3-Oxoisothiazolo[5,4-b]pyridines; J. heterocyclic. Chem, 22,         1353 (1985).     -   article A. Dunn, R. Norrie; Synthesis of pyrido-1,3-thiazines;         Zeitschrift fur chemie 1988, vol 28, n° 6, p 212/214.     -   S. Andreae; J. Parkt. Chem. 339 (1997) 152-158;     -   S. Gorsuch; Biorganic & Medicinal Chemistry 17 (2009) 467-474.     -   A. Monge et al; J. Heterocyclic Che. 25, 23 (1988).     -   M. Pregnolato; II Farmaco 55 (2000) 669-679.

Preferably, the compounds of the formula (I) or (I′) have the following meanings:

-   R₁ denotes a radical chosen from:     -   a) a hydrogen atom;     -   b) a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or unsaturated         C₂-C₁₀ alkyl group, optionally substituted with one or more OR₃         groups; -   R₂ denotes a radical chosen from:     -   a) a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or cyclic C₃-C₇         alkyl group, optionally interrupted with one or more oxygen         atoms, preferably one, and/or optionally containing one or more         groups, which may be identical or different, chosen from:         -   i) —OR₃,         -   ii) —NR₃R₄,         -   iii) —CONHR₃,         -   iv) —COOR₃     -   b) a phenyl group optionally substituted with one or more         hydroxyls and/or with one or more C₁-C₃ alkoxy radicals;     -   c) a saturated C₁-C₅ alkyl group substituted with a phenyl         radical optionally substituted with one or more hydroxyls or         with one or more C₁-C₃ alkoxy radicals; -   R₃ denoting a hydrogen atom or a saturated linear C₁-C₅ or branched     C₃-C₅ hydrocarbon-based group; -   R₄ denoting a hydrogen atom or a saturated linear C₁-C₅ or branched     C₃-C₅ hydrocarbon-based group;

and the salts thereof, the solvates thereof and the optical isomers thereof, and the racemates thereof.

Preferentially, the compounds of formula (I) or (I′) have the following meanings:

-   R₁ denotes a hydrogen atom or a linear C₁-C₄ alkyl radical     optionally substituted with one or more hydroxyl groups; -   R₂ denotes a radical chosen from:     -   a) a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or cyclic C₅-C₇         alkyl group, optionally interrupted with an oxygen atom and/or         optionally containing a —CONH₂ group and/or optionally         substituted with one or more hydroxyl groups;     -   b) a phenyl group;     -   c) a saturated C₁-C₅ alkyl group substituted with a phenyl         radical optionally substituted with one or more hydroxyl or         C₁-C₃ alkoxy radicals;

and also the salts thereof, the solvates thereof and the optical isomers thereof, and the racemates thereof.

More preferentially, the compounds of formula (I) or (I′) have the following meanings:

-   R₁ denotes a hydrogen atom or a C₁-C₄ hydroxyalkyl group; -   R₂ denotes a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or cyclic     C₅-C₆ alkyl hydrocarbon-based group, optionally interrupted with an     oxygen atom and/or optionally containing a —CONH₂ group and/or     optionally substituted with a hydroxyl group; a phenyl group; or a     saturated C₁-C₅ alkyl group substituted with a phenyl radical itself     optionally substituted with one or more hydroxyl or C₁-C₃ alkoxy     radicals;

and also the salts thereof, the solvates thereof and the optical isomers thereof, and the racemates thereof.

The subject of the invention is also the novel compounds of formulae (Ia) and (Ia′) corresponding to those of formula (I) or (I′) in which:

-   -   when R1 denotes a hydrogen atom, then R2 denotes a radical         chosen from unsaturated C₂-C₂₀ alkyls, cyclic C₇ alkyl radicals,         saturated linear C₁-C₂₀ or branched C₃-C₂₀ alkyls, substituted         with one or more identical or different —OR₃ groups, and         (C₁-C₂₀)alkylaryls substituted with one or more identical or         different —OR₃ groups, R₃ denoting a hydrogen atom or a         saturated linear C₁-C₅ or branched C₃-C₅ or unsaturated C₂-C₅         hydrocarbon-based group;     -   when R₁ denotes a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or         unsaturated C₂-C₁₀ alkyl group, optionally substituted with one         or more —OR₃ groups, then R₂ denotes a radical chosen from:

-   a) a saturated branched C₃-C₁₂ or cyclic C₃-C₇ alkyl group,     optionally interrupted with one or more oxygen atoms, preferably     one, and/or optionally containing one or more identical or different     —OR₃ groups,

-   R₃ denoting a hydrogen atom or an optionally hydroxylated, saturated     linear C₁-C₅ or branched C₃-C₅ hydrocarbon-based group;

and also the salts thereof, the optical isomers thereof and the racemates thereof.

Preferably, for the novel compounds of the formulae (Ia) and (Ia′):

-   -   when R1 denotes a hydrogen atom, then R2 denotes a radical         chosen from unsaturated C₂-C₂₀ alkyls, saturated linear C₁-C₂₀         or branched C₃-C₂₀ alkyls, substituted with one or more         identical or different —OR₃ groups, and (C₁-C₆)alkylphenyls         substituted with one or more identical or different —OR₃ groups,         R₃ denoting a hydrogen atom or a saturated linear C₁-C₅ or         branched C₃-C₅ or unsaturated C₂-C₅ hydrocarbon-based group;     -   when R1 denotes a saturated linear C₁-C₁₂ or branched C₃-C₁₀ or         unsaturated C₂-C₁₀ alkyl group, optionally substituted with one         or more —OR₃ groups, then R₂ denotes a radical chosen from:

-   a) a saturated branched C₃-C₁₂ or cyclic C₃-C₇ alkyl group,     optionally interrupted with one or more oxygen atoms, preferably     one, and/or optionally containing one or more identical or different     —OR₃ groups,

-   R₃ denoting a hydrogen atom or an optionally hydroxylated, saturated     linear C₁-C₅ or branched C₃-C₅ hydrocarbon-based group,

and also the salts thereof, the optical isomers thereof and the racemates thereof.

Preferably, for the novel compounds of formulae (Ia) and (Ia′):

-   -   when R₁ denotes a hydrogen atom, then R₂ denotes a radical         chosen from saturated linear C₁-C₂₀ or branched C₃-C₂₀ alkyls,         substituted with one or more identical or different —OR₃ groups,         and (C₁-C₆)alkylphenyls substituted with one or more identical         or different —OR₃ groups, R₃ denoting a hydrogen atom or a         saturated linear C₁-C₅ or branched C₃-C₅ or unsaturated C₂-C₅         hydrocarbon-based group;     -   when R₁ denotes a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or         unsaturated C₂-C₁₀ alkyl group, optionally substituted with one         or more —OR₃ groups, then R₂ denotes a radical chosen from:

-   a) a saturated branched C₃-C₁₂ or cyclic C₃-C₇ alkyl group,     optionally interrupted with one or more oxygen atoms, preferably     one, and/or optionally containing one or more identical or different     —OR₃ groups,

-   R₃ denoting a hydrogen atom or an optionally hydroxylated, saturated     linear C₁-C₅ or branched C₃-C₅ hydrocarbon-based group.

Preferably, for the novel compounds of formulae (Ia) and (Ia′):

-   R₁ denotes a hydrogen atom and R₂ denotes a radical chosen from: -   a) a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or cyclic C₅-C₇     alkyl group, substituted with one or more hydroxyl groups, and     optionally interrupted with an oxygen atom, or -   R₁ denotes a linear C₁-C₄ alkyl radical optionally substituted with     one or more hydroxyl groups; and R₂ denotes a radical chosen from: -   a) a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or cyclic C₅-C₇     alkyl group, substituted with one or more hydroxyl groups, and     optionally interrupted with an oxygen atom.

Preferentially, for the novel compounds of formulae (Ia) and (Ia′):

-   R₁ denotes a hydrogen atom and R₂ denotes a saturated linear C₁-C₁₀     or branched C₃-C₁₀ or cyclic C₅-C₆ alkyl hydrocarbon-based group,     optionally interrupted with an oxygen atom and optionally     substituted with a hydroxyl group, or -   R₁ denotes a C₁-C₄ hydroxyalkyl group; -   R₂ denotes a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or cyclic     C₅-C₆ alkyl hydrocarbon-based group, optionally interrupted with an     oxygen atom and optionally substituted with a hydroxyl group.

Among the compounds of formula (I), the following compounds are preferably used:

No. Structure Chemical name CAS No.  1

N-methyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 91859- 74-4  2

N-ethyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 91859- 75-5  3

N-isopropyl-2-thioxo- 1,2-dihydropyridine-3- carboxamide 91859- 76-6  4

N-propyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 330667- 56-6  5

N-(2-methylpropyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 1100027- 79-9  6

N-butyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 65282- 55-5  7

N-pentyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 330667- 57-7  8

N-octyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 91859- 77-7  9

N-nonyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 1031149- 44-6 10

N,N-dimethyl-2- mercaptonicotinamide 121650- 19-9 11

N-cyclopentyl-2- thioxo-1,2- dihydropyridine-3- carboxamide 1099928- 42-3 12

N-cyclohexyl-2-thioxo- 1,2-dihydropyridine-3- carboxamide 91859- 78-8 13

N-cycloheptyl-2- thioxo-1,2- dihydropyridine-3- carboxamide 451473- 73-7 14

N-phenyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 104857- 16-1 15

N-benzyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 91859- 79-9 16

N-[2-(4- methoxyphenyl)ethyl]- 2-thioxo-1,2- dihydropyridine-3- carboxamide 923682- 88-6 17

N-(3-ethoxypropyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 1061763- 97-02 18

N-(2-amino-2- oxoethyl)-2-thioxo-1,2- dihydropyridine-3- carboxamide 497262- 18-7 19

N-(2-hydroxyethyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 20

N,N-bis(2- hydroxyethyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 21

N-(2,3- dihydroxypropyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 22

N-(1,3- dihydroxypropan-2-yl)- 2-thioxo-1,2- dihydropyridine-3- carboxamide 23

N-ethyl-N-(2- hydroxyethyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 24

N-(3-hydroxypropyl)- 2-thioxo-1,2- dihydropyridine-3- carboxamide 25

N-[2-(2- hydroxyethoxy)ethyl]- 2-thioxo-1,2- dihydropyridine-3- carboxamide 26

N-(3-methoxypropyl)- 2-thioxo-1,2- dihydropyridine-3- carboxamide 27

N,N-diethyl 2- mercaptonicotinamide 121050- 20-2 28

Ethyl N-[(2-thioxo-1,2- dihydropyridin-3- yl)carbonyl]alaninate 29

Ethyl N-[(2-thioxo-1,2- dihydropyridin-3- yl)carbonyl]phenyl alaninate 30

N-[2- (dimethylamino)ethyl]- N-ethyl-2-thioxo-1,2- dihydropyridine-3- carboxamide

Among these compounds, the following compounds are more particularly preferred:

No. Structure Chemical name  1

N-methyl-2-thioxo- 1,2-dihydropyridine-3- carboxamide  2

N-ethyl-2-thioxo-1,2- dihydropyridine-3- carboxamide  3

N-isopropyl-2-thioxo- 1,2-dihydropyridine-3- carboxamide  4

N-propyl-2-thioxo- 1,2-dihydropyridine-3- carboxamide  5

N-(2-methylpropyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide  6

N-butyl-2-thioxo-1,2- dihydropyridine-3- carboxamide  7

N-pentyl-2-thioxo-1,2- dihydropyridine-3- carboxamide 11

N-cyclopentyl-2- thioxo-1,2- dihydropyridine-3- carboxamide 12

N-cyclohexyl-2- thioxo-1,2- dihydropyridine-3- carboxamide 13

N-cycloheptyl-2- thioxo-1,2- dihydropyridine-3- carboxamide 15

N-benzyl-2-thioxo- 1,2-dihydropyridine-3- carboxamide 16

N-[2-(4- methoxyphenyl)ethyl]- 2-thioxo-1,2- dihydropyridine-3- carboxamide 19

N-(2-hydroxyethyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 20

N,N-bis(2- hydroxyethyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 21

N-(2,3- dihydroxypropyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 23

N-ethyl-N-(2- hydroxyethyl)-2- thioxo-1,2- dihydropyridine-3- carboxamide 27

N,N-diethyl 2- mercaptonicotinamide

and also the salts thereof, the optical isomers thereof and the solvates thereof.

Compounds 1 and 10 are described in application EP-A-298752 as synthesis intermediates.

Compounds 2 to 8, 11 and 12 are described in FR-A-2555450.

Compound 14 is described in the article A. Monge, V. Martinez-Merino; Synthesis of 2-substituted 3-Oxoisothiazolo[5,4-b]pyridines; J. heterocyclic. Chem, 22, 1353 (1985).

Compounds 4, 6, 7 and 15 are described in the article A. Dunn, R. Norrie; Synthesis of pyrido-1,3-thiazines; Zeitschrift fur chemie 1988, vol 28, n° 6, p 212/214.

Compound 14 is described in the article A. Monge, V. Martinez-Merino; Synthesis of 2-substituted 3-Oxoisothiazolo[5,4-b]pyridines; J. heterocyclic. Chem, 22, 1353 (1985).

Compound 18 is described in WO-A-03/014062.

Compound 27 is described in EP 298752.

Compounds 2, 7, 12, 16, 21 and 27 are the most particularly preferred.

The compounds of formula (I) and/or (I′) according to the invention are of quite particular use in the cosmetics field.

The composition used according to the invention comprises a compound of formula (I) and/or (I′) as described above, in a physiologically acceptable medium.

The compound (I) and/or (I′) can be present in the composition used according to the invention in an amount which can be between 0.01 and 10% by weight, preferably between 0.1 and 5% by weight, in particular from 0.5 to 3% by weight, relative to the total weight of the composition.

The term “physiologically acceptable medium” is understood to mean a medium that is compatible with keratin materials of human beings, such as the skin of the body or of the face, the lips, the mucous membranes, the eyelashes, the nails, the scalp and/or the hair.

The composition used according to the invention may thus comprise all the adjuvants which are commonly employed in the cosmetics field.

Mention may in particular be made of water; organic solvents, in particular C₂-C₆ alcohols; oils, in particular hydrocarbon-based oils, silicone oils; waxes, pigments, fillers, dyes, surfactants, emulsifiers; cosmetic active agents, UV screens, polymers, thickeners, preservatives, fragrances, bactericides, odour absorbers and antioxidants.

These optional cosmetic adjuvants may be present in the composition in a proportion of from 0.001 to 80% by weight, in particular 0.1 to 40% by weight, relative to the total weight of the composition. In any event, these adjuvants, and also the proportions thereof, will be chosen by those skilled in the art in such a way that the advantageous properties of the compounds according to the invention are not, or not substantially, impaired by the envisaged addition.

As active agents, it will be advantageous to introduce into the composition used according to the invention at least one compound chosen from: desquamating agents; calmatives; organic or inorganic photoprotective agents, moisturizers; depigmenting or propigmenting agents; anti-glycation agents; NO-synthase inhibitors; agents for stimulating the synthesis of dermal or epidermal macromolecules and/or preventing degradation thereof; agents for stimulating fibroblast and/or keratinocyte proliferation or stimulating keratinocyte differentiation; muscle relaxants and/or dermo-decontracting agents; tensioning agents; anti-pollution agents and/or free-radical scavengers; agents that act on the microcirculation; agents that act on the energy metabolism of cells; and mixtures thereof.

Examples of such additional compounds are: retinol and derivatives thereof such as retinyl palmitate; ascorbic acid and derivatives thereof such as magnesium ascorbyl phosphate and ascorbyl glucoside; tocopherol and derivatives thereof such as tocopheryl acetate; nicotinic acid and precursors thereof such as nicotinamide; ubiquinone; glutathione and precursors thereof such as L-2-oxothiazolidine-4-carboxylic acid; plant extracts and in particular plant proteins and hydrolysates thereof, and also plant hormones; marine extracts such as algal extracts; bacterial extracts; sapogenins such as diosgenin and wild yam extracts containing same; ceramides; hydroxy acids such as salicylic acid and 5-n-octanoylsalicylic acid; resveratrol; oligopeptides and pseudodipeptides and acyl derivatives thereof; manganese salts and magnesium salts, in particular the gluconates; and mixtures thereof.

The term “desquamating agent” is intended to mean any compound capable of acting:

-   -   either directly on desquamation by promoting exfoliation, such         as β-hydroxy acids, in particular salicylic acid and derivatives         thereof (including 5-n-octanoyl-salicylic acid); α-hydroxy         acids, such as glycolic acid, citric acid, lactic acid, tartaric         acid, malic acid or mandelic acid; urea; gentisic acid;         oligofucoses; cinnamic acid; Saphora japonica extract;         resveratrol;     -   or on the enzymes involved in the desquamation or degradation of         corneodesmosomes, glycosidases, stratum corneum chymotryptic         enzyme (SCCE) or even other proteases (trypsin,         chymotrypsin-like). Mention ay be made of agents for chelating         mineral salts: EDTA; N-acyl-N,N′,N′-ethylenediaminetriacetic         acid; am inosulphonic compounds and in particular (N-2         hydroxyethylpiperazine-N-2-ethane)sulphonic acid (HEPES);         derivatives of 2-oxothiazolidine-4-carboxylic acid         (procysteine); derivatives of alpha-amino acids of glycine type         (as described in EP-0 852 949, and also sodium methyl glycine         diacetate sold by BASF under the trade name Trilon M); honey;         sugar derivatives such as O-octanoyl-6-D-maltose and         N-acetylglucosamine.

The desquamating agents are generally present in the composition according to the invention in proportions ranging from 0.01 to 15% by weight, preferably ranging from 0.1 to 10% by weight, relative to the total weight of the composition.

As calmatives that can be used in the composition according to the invention, mention may be made of: pentacyclic triterpenes and extracts of plants (for example Glycyrrhiza glabra) containing them, for instance β-glycyrrhetinic acid and salts and/or derivatives thereof (glycyrrhetinic acid monoglucuronide, stearyl glycyrrhetinate, 3-stearoyloxyglycyrrhetic acid), ursolic acid and salts thereof, oleanolic acid and salts thereof, betulinic acid and salts thereof, an extract of Paeonia suffruticosa and/or lactiflora, salicylic acid salts and in particular zinc salicylate, phycosaccharides from the company Codif, an extract of Laminaria saccharina, canola oil, bisabolol and camomile extracts, allantoin, Sepivital EPC (phosphoric diester of vitamin E and C) from SEPPIC, omega-3 unsaturated oils such as musk rose oil, blackcurrant oil, ecchium oil, fish oil, plankton extracts, capryloylglycine, Seppicalm VG (sodium palmitoylproline and Nymphea alba) from SEPPIC, an extract of Pygeum, an extract of Bosweffia serrata, an extract of Centipeda cunnighami, an extract of Helianthus annuus, an extract of Linum usitatissimum, tocotrienols, extracts of Cola nitida, piperonal, an extract of clove, an extract of Epilobium angustifolium, aloe vera, an extract of Bacopa moniera, phytosterols, cortisone, hydrocortisone, indomethacin and betamethasone.

The calmatives are generally present in the composition used according to the invention in proportions ranging from 0.01 to 15% by weight, preferably ranging from 0.1 to 10% by weight, relative to the total weight of the composition.

The organic photoprotective agents are in particular chosen from anthranilates; cinnamic derivatives; dibenzoylmethane derivatives; salicylic derivatives, camphor derivatives; triazine derivatives such as those described in patent applications U.S. Pat. No. 4,367,390, EP863145, EP517104, EP570838, EP796851, EP775698, EP878469, EP933376, EP507691, EP507692, EP790243 and EP944624; benzophenone derivatives; β,β-diphenylacrylate derivatives; benzotriazole derivatives; benzalmalonate derivatives; benzimidazole derivatives; imidazolines; bis-benzoazolyl derivatives as described in patents EP669323 and U.S. Pat. No. 2,463,264; p-aminobenzoic acid (PABA) derivatives; methylenebis(hydroxyphenylbenzotriazole) derivatives as described in applications U.S. Pat. No. 5,237,071, U.S. Pat. No. 5,166,355, GB2303549, DE19726184 and EP893119; screening polymers and screening silicones such as those described in particular in application WO-93/04665; and α-alkylstyrene-derived dimers such as those described in patent application DE 19855649.

The inorganic photoprotective agents can in particular be chosen from coated or uncoated metal oxide pigments or nanopigments (average size of the primary particles generally between 5 nm and 100 nm, preferably between 10 nm and 50 nm), for instance nanopigments of titanium oxide (amorphous or crystallized in rutile and/or anatase form), of iron oxide, of zinc oxide, of zirconium oxide or cerium oxide, which are all well-known UV photoprotective agents. Conventional coating agents are, moreover, alumina and/or aluminium stearate. Such coated or uncoated metal oxide nanopigments are in particular described in patent applications EP518772 and EP518773.

The photoprotective agents are generally present in the composition used according to the invention in proportions ranging from 0.1 to 20% by weight, preferably ranging from 0.2 to 15% by weight, relative to the total weight of the composition.

The composition used according to the invention may be in any of the galenical forms normally used in the cosmetics field, and in particular in the form of an optionally gelled aqueous or aqueous-alcoholic solution, a dispersion, optionally a two-phase dispersion, of the lotion type, an oil-in-water or water-in-oil or multiple (W/O/W or O/W/O) emulsion, an aqueous gel, a dispersion of oil in an aqueous phase by means of spherules, it being possible for these spherules to be polymeric nanoparticles such as nanospheres and nanocapsules or, better still, lipid vesicles of ionic and/or nonionic type; or aqueous or oily gels. These compositions are prepared according to the usual methods. According to this invention, a composition in the form of an emulsion, in particular an oil-in-water emulsion, is preferably used.

The composition used according to the invention may constitute a skincare composition, and in particular a cleansing, protecting, treatment or care cream for the face, for the hands, for the feet, for the major anatomical folds or for the body (for example, day creams, night creams, makeup-removing creams, foundation creams, antisun creams); a fluid foundation, a makeup-removing milk, a protective or care body milk or an antisun milk; a skincare lotion, gel or foam, such as a cleansing lotion.

The invention is illustrated in greater detail by the following nonlimiting examples.

EXAMPLES 1 TO 4 Demonstration of the Activity on Constitutive Melanogenesis

A biological test demonstrated the depigmenting activity of 7 compounds of formula (I) (compounds 2, 7, 12, 16, 19, 21 and 27).

The modulatory effect of each compound on melanogenesis was measured according to the method described in FR-A-2734825 and also in the article by R. Schmidt, P. Krien and M. Régnier, Anal. Bichem., 235(2), 113-18, 1996. This test is carried out on a coculture of keratinocytes and melanocytes.

For the compounds tested, the following were determined:

-   -   the cytotoxicity, by estimating leucine incorporation,     -   the inhibitory activity on melanin synthesis, by estimating the         ratio of thiouracil incorporation to leucine incorporation,         relative to 100% of the control (the control corresponds to the         test carried out without test compound). The 1050 values         (concentration for which 50% of the melanin synthesis is         inhibited) were determined.

The test was also carried out with arbutin, niacinamide and kojic acid, which are known depigmenting compounds.

The results are collated in the following table:

Cyto- toxicity on co- Compound culture IC50 Arbutin Non- Not attained cytotoxic (or greater than 500 μM) Kojic acid 100 μM Not attained (or greater than 500 μM) Niacinamide Non- Not attained cytotoxic

Non- cytotoxic 4.9 μM

Non- cytotoxic 37 μM

100 μM 25 μM

Non- cytotoxic 32 μM

Non- cytotoxic 29 μM

Non- cytotoxic 410 μM

Non- cytotoxic 128 μM

Compounds 2, 7, 12, 16, 19, 21 and 27 therefore demonstrate their efficacy in inhibiting melanogenesis and are, moreover, more effective than arbutin, kojic acid and niacinamide.

Compound 2 is the most effective compound.

EXAMPLE 5

A depigmenting gel for the skin is prepared, comprising (% by weight):

Compound 2 2% Carbomer (Carbopol 981 from Lubrizol) 1% preservative qs water qs 100%

When applied to the skin, the composition makes it possible to fade out brown marks.

A similar composition is prepared with compound 3 or compound 11 or compound 16. 

The invention claimed is:
 1. A nontherapeutic cosmetic process for depigmenting, lightening and/or whitening keratin materials, comprising: selecting a human subject exhibiting brownish pigmentation marks or senescence marks or who wish to combat the appearance of a brownish color arising from melanogenesis, and applying to a keratin material of the subject an effective amount of at least one compound of formula (I):

or a tautomer thereof of formula (I′):

wherein: R₁ and R₂, which may be identical or different, represent a radical selected from the group consisting of: a) a hydrogen atom; b) a saturated linear C₁-C₂₀ or branched C₃-C₂₀ or unsaturated C₂-C₂₀ alkyl group, optionally interrupted with one or more heteroatoms selected from the group consisting of N, S and O and/or optionally substituted with one or more groups, optionally identical or different, selected from the group consisting of i) —OR₃, ii) —SR₃, iii) —NR₃R₄, iv) —CONHR₃, v) —COOR₃, and vi) a C₅-C₁₂ aryl group optionally substituted with one or more hydroxyls and/or with one or more C₁-C₈ alkoxy radicals; c) a saturated C₁-C₈ alkyl group substituted with a C₅-C₁₂ aryl radical optionally substituted with one or more hydroxyls and/or with one or more C₁-C₈ alkoxy radicals; and d) a phenyl group optionally substituted with one or more hydroxyls and/or with one or more C₁-C₈ alkoxy radicals; R₃ represents a hydrogen atom or a saturated linear C₁-C₅ or branched C₃-C₅ or unsaturated C₂-C₅ hydrocarbon-based group; and R₄ represents a hydrogen atom, a saturated linear C₁-C₅ or branched C₃-C₅ hydrocarbon-based group, or an acetyl group; such that R₁ and R₂ optionally form, with the nitrogen atom which bears them, a ring selected from the group consisting of pyrrolidine, pyrroline, piperidine, piperazine, morpholine, thiomorpholine and azepine, or a salt thereof, an optical isomer thereof or a racemate thereof.
 2. The process of claim 1, wherein: R₁ represents a radical selected from the group consisting of: a) a hydrogen atom; and b) a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or unsaturated C₂-C₁₀ alkyl group, optionally substituted with one or more OR₃ groups; R₂ represents a radical selected from the group consisting of: a) a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or cyclic C₃-C₇ alkyl group, optionally interrupted with one or more oxygen atoms, and/or optionally containing one or more groups, which may be identical or different, selected from the group consisting of i) —OR₃, ii) —NR₃R₄, iii) —CONHR₃, and iv) —COOR₃; b) a phenyl group optionally substituted with one or more hydroxyls and/or with one or more C₁-C₃ alkoxy radicals; and c) a saturated C₁-C₅ alkyl group substituted with a phenyl radical optionally substituted with one or more hydroxyls and/or with one or more C₁-C₃ alkoxy radicals; R₃ represents a hydrogen atom or a saturated linear C₁-C₅ or branched C₃-C₅ hydrocarbon-based group; and R₄ represents a hydrogen atom or a saturated linear C₁-C₅ or branched C₃-C₅ hydrocarbon-based group.
 3. The process of claim 1, wherein: R₁ represents a hydrogen atom or a linear C₁-C₄ alkyl radical optionally substituted with one or more hydroxyl groups; R₂ represents a radical selected from the group consisting of a) a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or cyclic C₅-C₇ alkyl group, optionally interrupted with an oxygen atom and/or optionally containing a —CONH₂ group and/or optionally substituted with one or more hydroxyl groups; b) a phenyl group; and c) a saturated C₁-C₅ alkyl group substituted with a phenyl radical optionally substituted with one or more hydroxyl or C₁-C₃ alkoxy radicals.
 4. The process of claim 1, wherein: R₁ represents a hydrogen atom or a C₁-C₄ hydroxyalkyl group; and R₂ represents a saturated linear C₁-C₁₀ or branched C₃-C₁₀ or cyclic C₅-C₆ alkyl hydrocarbon-based group, optionally interrupted with an oxygen atom and/or optionally containing a —CONH₂ group and/or optionally substituted with a hydroxyl group; a phenyl group; or a saturated C₁-C₅ alkyl group substituted with a phenyl radical itself optionally substituted with one or more hydroxyl or C₁-C₃ alkoxy radicals.
 5. The process of claim 1, wherein the compound of formula (I) is selected from the group consisting of following N-methyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-ethyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-isopropyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-propyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(2-methylpropyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-butyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-pentyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-octyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-nonyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N,N-dimethyl-2-mercaptonicotinamide; N-cyclopentyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-cyclohexyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-cycloheptyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-phenyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-benzyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-[2-(4-methoxyphenyl)ethyl]-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(3 -ethoxypropyl)-2-thioxo-1,2-dihydropyridine-3 -carboxamide; N-(2-amino-2-oxoethyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(2-hydroxyethyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N,N-bis(2-hydroxyethyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(2,3-dihydroxypropyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(1,3-dihydroxypropan-2-yl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-ethyl-N-(2-hydroxyethyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-[2-(2-hydroxyethoxy)ethyl]-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(3 -hydroxypropyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-[2-(2-hydroxyethoxy)ethyl]-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(3 -methoxypropyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N,N-diethyl 2-mercaptonicotinamide; Ethyl N-[(2-thioxo-1,2-dihydropyridin-3-yOcarbonyl]alaninate; Ethyl N-[(2-thioxo-1,2-dihydropyridin-3-yOcarbonyl]phenyl alaninate; and N-[2-(dimethylamino)ethyl]-N-ethyl-2-thioxo-1,2-dihydropyridine-3-carboxamide.
 6. The process of claim 1, wherein the compound of formula (I) is selected from the group consisting of the following N-methyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-ethyl-2-thioxo-1,2-dihydropyridine-3-carboxamide ; N-isopropyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-propyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(2-methylpropyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-butyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-pentyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-cyclopentyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-cyclohexyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-cycloheptyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-benzyl-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-[2-(4-methoxyphenyl)ethyl]-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(2-hydroxyethyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N,N-bis(2-hydroxyethyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-(2,3-dihydroxypropyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; N-ethyl-N-(2-hydroxyethyl)-2-thioxo-1,2-dihydropyridine-3-carboxamide; and N,N-diethyl 2-mercaptonicotinamide.
 7. The process of claim 1, wherein the compound of formula (I) or the tautomer thereof of formula (I′) is applied in the form of a composition, wherein the composition contains 0.01 to 10% by weight, based on the total weight of the composition of the compound of formula (I).
 8. The process of claim 7, wherein the composition further comprises at least one adjuvant selected from the group consisting of: water; an organic solvent; a carbon-based and/or silicone oil, of mineral, animal and/or plant origin; a wax; a pigment; a filler; a dye; a surfactant; an emulsifier; a co-emulsifer; a cosmetic or dermatological active agent; a UV screen; a hydrophilic or lipophilic gelling agent; a thickener; a preservative; a fragrance; a bactericide; a ceramide; an odor absorber; and an antioxidant.
 9. The process of claim 7, wherein the composition further comprises at least one active agent selected from the group consisting of: a desquamating agent; a calmative; an organic or inorganic photoprotective agent agents; a moisturizer; a depigmenting or propigmenting agent; an anti-glycation agent; a NO-synthase inhibitor; an agent for stimulating the synthesis of dermal or epidermal macromolecules and/or preventing degradation thereof; an agent for stimulating fibroblast and/or keratinocyte proliferation and/or stimulating keratinocyte differentiation; a muscle relaxant and/or dermo-decontracting agent; a tensioning agent; an anti-pollution agent; a free-radical scavenger; an agent that acts on the microcirculation; an agent that acts on the energy metabolism of cells; and mixtures thereof. 